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Discussion Starter #21
If you've never replaced the O2 sensors and your vehicle has over 75K miles, I'd say it's safe to go ahead and replace them anyway.

Are you getting any codes?

@VWandDodge

My Mazda3 has around 130,000 miles. So I guess I could swap out the O2 sensors. Any recommendation on brand? NTK or Denso?

Yes I did get a fault code about a week ago. It was a P2187 fault code and I had a P2187 pending code as well. P2187 is "system too lean at idle (bank 1)".

I checked for vacuum leaks but the only thing that looked suspect to me was my MAF o-ring was a bit stretched out. I've ordered a new one and will get it installed once I get it in hand.
 

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Would a video of the issue help?

I'm pretty sure the shaking and vibration is loud enough to be picked up on cell phone video.

I will try and take one in the next day or so.
A video would be great. It sounds like you have a mis-fire. The first possible cause listed out of the many listed in the service manual for a P2187 is mis-fire. Wonder if you have a bad coil or plug? That would account for the vibration as the vehicle is only running on 3 cylinders.

Also, the number one repair listed under the real fixes tab on Mitchell Prodemand is a bad canister purge valve/solenoid.
 

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@VWandDodge

My Mazda3 has around 130,000 miles. So I guess I could swap out the O2 sensors. Any recommendation on brand? NTK or Denso?

Yes I did get a fault code about a week ago. It was a P2187 fault code and I had a P2187 pending code as well. P2187 is "system too lean at idle (bank 1)".

I checked for vacuum leaks but the only thing that looked suspect to me was my MAF o-ring was a bit stretched out. I've ordered a new one and will get it installed once I get it in hand.
According to RockAuto, Denso is the OE part number, so I'd stick with them. I don't think NTK would be an issue as it's a reliable brand. Over in the Dodge Ram world, the Second Gen Magnum engines only played nice with OE NTK O2 sensors .
 

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Discussion Starter #24
Would a video of the issue help?

I'm pretty sure the shaking and vibration is loud enough to be picked up on cell phone video.

I will try and take one in the next day or so.
A video would be great. It sounds like you have a mis-fire. The first possible cause listed out of the many listed in the service manual for a P2187 is mis-fire. Wonder if you have a bad coil or plug? That would account for the vibration as the vehicle is only running on 3 cylinders.

Also, the number one repair listed under the real fixes tab on Mitchell Prodemand is a bad canister purge valve/solenoid.
@rickkari

Here is the link to video: https://youtu.be/Qag2X9ePcZE

This weekend I hooked a spark plug tester up to each cylinder and tested them while idling and also revving in park. Nothing really looked out of the ordinary, so if I do have a misfire then it's happening in gear at that certain rpm under load. Hope the video helps to figure out what this is!
 

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Are you certain you don't have worn tie rod ends, worn ball joints, or bad bushings?
 

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Discussion Starter #26
@VWandDodge

I'm not 100% certain, but I hadn't really considered that due to the fact that the car feels fine suspension and steering wise. No knocks, creaks, rattles or etc. Just the unexplained vibration at that specific RPM.

But I can definitely check things out! I'll jack it up and wiggle on the tires and see if there's any play and also visually take a look at the tie rods and control arms.
 

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Discussion Starter #27
Last night I got the replacement MAF o-ring in the mail and installed it. The old one was pretty stretched out and didn't seem like it was sealing very good. The new o-ring did help out a small bit. It's marginal, but I do feel a difference in idle and throttle response. But the major vibration that occurs in 5th gear around 1500RPM, while cruising along at 40mph, is still there. It's really like the engine is chugging or dropping out for some reason. Low fuel, low air, I don't know. Feels starved at that specific RPM or speed.

Beginning to think that maybe the issue is the product of several things: lazy o2 sensors, worn out throttle body, clogged EGR, etc. Seems like I have several options to try, but I just hate to throw parts and money at it and hope it fixes it.

Once the cold weather breaks in the next few days, I will try to get under the car and inspect tie rods, control arms, and CV joints.

One way or another I'm gonna figure this out!!!
 

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Last night I got the replacement MAF o-ring in the mail and installed it. The old one was pretty stretched out and didn't seem like it was sealing very good. The new o-ring did help out a small bit. It's marginal, but I do feel a difference in idle and throttle response. But the major vibration that occurs in 5th gear around 1500RPM, while cruising along at 40mph, is still there. It's really like the engine is chugging or dropping out for some reason. Low fuel, low air, I don't know. Feels starved at that specific RPM or speed.

Beginning to think that maybe the issue is the product of several things: lazy o2 sensors, worn out throttle body, clogged EGR, etc. Seems like I have several options to try, but I just hate to throw parts and money at it and hope it fixes it.

Once the cold weather breaks in the next few days, I will try to get under the car and inspect tie rods, control arms, and CV joints.

One way or another I'm gonna figure this out!!!
Interesting, and makes complete sense. The emissions system can create a lot of whacky conditions like you've noted when it's compromised. Please keep us posted with your progress. You're definitely not throwing parts at it at this point. More like correcting issues and addressing maintenance items you didn't know mattered.
 

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Discussion Starter #29
So update on the shaking/vibration issue.

I swapped out the O2 sensors and put on a brand new OEM throttle body I was able to get a good price. I had planned to replace the EGR valve, but one of the bolts holding it on was just way too hard to get to and I didn't feel like dumping a lot of my coolant out as it helps to pull a big radiator hose thats in the way.

The result was: not much difference or improvement. My car does idle really good, but the vibration/shaking/shudder remains when I reach cruising speed on city streets (40-45 MPH). Not sure how to describe it any better. It's mainly occurring when my foot is keeping a steady and light pressure on the gas pedal. RPMS will be fine and constant, then they drop a bit and the car starts vibrating/shaking and kind of feels like its bogging down. If I let off the gas or goose the gas pedal, it goes away.

I'm thinking now that my best bet is to take it in somewhere and get the coils/plugs and injectors professionally tested. Maybe there's a way I get the fuel pump and fuel filter tested too?

Let me know if there is anything else to try! I just want my car to drive normal again!
 

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So update on the shaking/vibration issue.

I swapped out the O2 sensors and put on a brand new OEM throttle body I was able to get a good price. I had planned to replace the EGR valve, but one of the bolts holding it on was just way too hard to get to and I didn't feel like dumping a lot of my coolant out as it helps to pull a big radiator hose thats in the way.

The result was: not much difference or improvement. My car does idle really good, but the vibration/shaking/shudder remains when I reach cruising speed on city streets (40-45 MPH). Not sure how to describe it any better. It's mainly occurring when my foot is keeping a steady and light pressure on the gas pedal. RPMS will be fine and constant, then they drop a bit and the car starts vibrating/shaking and kind of feels like its bogging down. If I let off the gas or goose the gas pedal, it goes away.

I'm thinking now that my best bet is to take it in somewhere and get the coils/plugs and injectors professionally tested. Maybe there's a way I get the fuel pump and fuel filter tested too?

Let me know if there is anything else to try! I just want my car to drive normal again!
I'm wondering if there is a cracked/broken vacuum line. The fuel pump and filter are a one-piece setup that delivers constant pressure. I don't see that being an issue.
 

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My car does idle really good, but the vibration/shaking/shudder remains when I reach cruising speed on city streets (40-45 MPH). Not sure how to describe it any better. It's mainly occurring when my foot is keeping a steady and light pressure on the gas pedal. RPMS will be fine and constant, then they drop a bit and the car starts vibrating/shaking and kind of feels like its bogging down. If I let off the gas or goose the gas pedal, it goes away.
Sounds like you are describing a bad torque converter lock up shudder issue symptom that is due to a bad torque converter. Just diagnosed one on a 2012 Camry the other day. You described the exact symptoms that it had. I have no experience diagnosing Mazda lock up issues, but it sounds like it by your description.
 

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.... I'm thinking now that my best bet is to take it in somewhere and get the coils/plugs and injectors professionally tested. Maybe there's a way I get the fuel pump and fuel filter tested too?

Let me know if there is anything else to try! I just want my car to drive normal again!
IMO you should have been using an OBD realtime data stream reader quite a while ago in this process. There have been lean codes set, and getting some key values (such as fuel trims) might be really helpful in diagnosing what the issue is. In addition to realtime data stream, the freeze frame data, captured at the time the code is set, can be very helpful as well. One fairly inexpensive and very popular realtime OBD tool is Torque for Android, although there are other choices as well, including off-the-shelf units.

And one other thing you can try is to add a bottle of Techron complete fuel system cleaner to your next tank of gas. Not saying this will fix your vehicle's issue, only that it's never a bad thing to do (i.e. routine maintenance), and MIGHT result in some improvement.

And my final item is the link below on a known MAF wiring issue with Mazda 3. However, the symptom in this link is rich running, which is opposite of what yours has been getting. But even though it doesn't sound like a hit, I'd want to check it out, simply because it's a known problem that's in the same ballpark.

https://www.mazda3forums.com/122-stock-issues/681713-maf-harness-connector-replacement.html
 

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Discussion Starter #33
Whatever improvement I had from replacing the throttle body and O2 sensors is gone now. My car is back to driving really horrible. Jumpy idle, vibrations at specific RPMs, jerky acceleration.

Seems like the car drives somewhat better after resetting the computer, but once everything is re-learned it goes back to the way it was driving before.

Not sure what else to try. So I think I will be taking it in to the Mazda Dealership and go from there.
 

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Discussion Starter #34
I finally got this issue fixed. The local mazda dealership found out that the bracket that goes between the rear motor mount and the transmission was completely trashed. They put a new one on and my car drives like it's brand new now. Glad I got it figured out.

Attached is a picture of the part they replaced. Hope this helps anyone that has the same problem!
 

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Glad you posted a resolution. Broken brackets will do it every time.
 
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